I'm a bit puzzled by a certain behavior with dates. (R version 3.1.1)
> temp1 <- as.Date(1:2, origin="2000/5/3")
> temp1
[1] "2000-05-04" "2000-05-05"
> temp2 <- as.POSIXct(temp1)
> temp2
[1] "2000-05-03 19:00:00 CDT" "2000-05-04 19:00:00 CDT"
So far so good. On 5/4, midnight in Greenwich it was 19:00 on 5/3 in my time zone. The
manual page has a clear explanation of what goes on.
> c(temp1, temp2)
[1] "2000-05-04" "2000-05-05" "2623237-10-15" "2623474-05-06"
> class(c(temp1, temp2))
[1] "Date"
> c(temp2, temp1)
[1] "2000-05-03 19:00:00 CDT" "2000-05-04 19:00:00 CDT"
[3] "1969-12-31 21:04:41 CST" "1969-12-31 21:04:42 CST"
> class(c(temp2, temp1))
[1] "POSIXct" "POSIXt"
I would have expected c() to determine a common class, somehow, then do the conversion and
concatonate. That is obviously not what happens. I've read the manual page but I must be
missing something. I make no claim that R is broken, mistaken, or otherwise deficient,
only that my understanding is so.
Could someone illuminate?
Terry T.
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